1. Field of the Invention
The present invention relates to an auto-focusing device used in cameras and the like.
2. Description of the Related Art
It is well known to provide automatic focus adjustment in cameras and the like. Cameras which provide auto-focusing operations, typically perform lens movement or drive operations starting from pre-set positions and directions during focusing operations in order to eliminate the influence of play or extraneous movement in a camera's focusing optical system. One such typical auto-focusing apparatus is disclosed in Japanese Patent Publication No. 63-144334.
Typical auto-focusing apparatus of the types briefly mentioned above and described in the cited Japanese Patent Publication No. 63-144334 are riddied with numerous problems. For example, conventional auto-focusing apparatus are devised so that they cause a lens barrel structure to return to an initial starting position after driving a lens past its focal point. Moreover, in the case where lens drive operations are performed starting from positions and directions which are opposite to an in-focus position, performance of quick and smooth focusing is extremely difficult.
In order to solve the aforementioned problem, it is conceivable that the influence of play or extraneous movement could be eliminated by inserting an energizing member, such as a spring, between a lens' anchored barrel and its support member which supports the focusing optical system. Such configurations, however, result in a lower drive capacity when a focusing optical system is driven in the direction from an infinity position to a close-range position and when the focusing optical system is driven in opposite directions.
In addition to the aforementioned problem, there is another problem which is typically seen in auto-focusing apparatus. More particularly, when there is a forward return disparity in the drive capacity of an auto-focusing apparatus, a separate problem develops in that it often becomes difficult to stop the focusing optical system at the target position quickly and accurately.